What is Roof Flashing?
Roof flashing is a thin material—typically galvanized steel—that professional roofers use to direct water away from the critical areas of the roof. It is typically wherever the roof plan meets a vertical surface, like a dormer or a wall.
Roof Flashing Types
- Continuous
- Base
- Counter
- Step
- Skylight
- Valley
- Drip Edges
- Kickout
The Basics of Roof Flashing Installation
The flashing is installed to surround the features of the roof, such as chimneys, vents, and skylights. Water should then run down the side of the flashing and be directed to the shingles instead of finding a way into the roof deck.
The Purpose of Flashing
Without the roof flashing against those walls, water would slowly drip into the space between the roof and wall and even potentially into the home.
So, what do you do when you need roof flashing? Knowing the different types and the techniques to implement can be helpful.
Roof Flashing Types
There are numerous types of roof flashing to choose from. Check out some examples below:
- Continuous Flashing. It is also known as “apron flashing” because it acts similarly to an apron. It is a long, single piece of metal used to carry the water down to the shingles below.
- Base Flashing. Some roof features, like chimneys, require two pieces of flashing to ensure the rain always meets a flashing surface to direct it downward. Not only that, it is notoriously difficult to install flashing around a chimney.
- Counter Flashing. Placed opposite the base flashing or above the base flashing. Counter flashing completes the team with the aforementioned base flashing.
- Step Flashing. A rectangular piece of flashing bent 90 degrees in the middle, generally used for wall flashing. In this instance, multiple pieces of flashing will be installed as layers with the shingles to ensure the water flows away from the wall.
- Skylight Flashing. Some skylight manufacturers include flashing with their products, but others require you to create or purchase it separately. Knowing which option you have beforehand is helpful.
- Valley Flashing. Any open valleys on your roof have metal flashing in order to protect this area, which is a critical area of the roof.
- Drip Edges. At the edge of the roof, there is a thin metal flashing that allows water to drip off the roof without damaging the home or causing a pesky leak that can cause further damage to the roof or home.
- Kickout Flashing. Roofing contractors generally need something to bridge the gap between where the step flashing comes to an end and where the gutter begins. This kind of flashing is used to direct water away from the wall and down into the gutter.
Roof Flashing Materials
You also need to be aware of a few different roofing materials. In the past, these would have been lead or lead-coated materials. Now, professionals throughout North America have switched to one of three materials.
Aluminum Flashing
Aluminum is generally easy for roofers to form and quite lightweight. However, it has to be coated if it is going to be used with masonry and concrete since plain aluminum degrades and reacts when it makes contact with alkaline surfaces.
Copper Roof Flashing
Copper takes soldering well and is also malleable, highly durable, and tends to have a longer-lasting life. On the other hand, there is some discoloring in the patina, which can vary depending on the homeowner. Copper flashing is routinely found around chimneys.
Steel Flashing
Steel is the most popular choice for flashing. In addition to aesthetic value, it is also malleable and corrosion-resistant when galvanized.
Be aware of building codes that may require or disallow a specific material. Have your roofing contractor look into this so that you are covered.
Identifying Flashing Types
There are quite a few types of roof flashing, nearly as many as parts to the roof. Each roof feature requires protection, hence the many different types of roof flashing.
Longer pieces of continuous flashing have trouble flexing as the home contracts and expands during the changing of the seasons. If left alone, it could warp or break and fail to keep that water out. If using longer pieces, they should have built-in expansion joints so that they can move as the home does.
Another benefit to two-part flashing is that when the roofing materials expand and contract with the weather, those two pieces can move, so the system stays secure.
Roof Flashing Techniques
So, how do you properly install roof flashing? Here are a few helpful techniques.
Step Flashing
The best place for step flashing is where the roof face meets a wall, such as where the dormer projects out from the roof. In a spot like this, it is entirely possible that water could flow down the wall and past the shingles into the building below.
Plumbing Vent Boot Flashing
Simply put, vent flashing has a cylindrical piece of flashing that fits around the vent itself. These shingles are installed over the base or the boot. The height of the boot is meant to force water to run around the vent itself.
Counter Flashing
Counter-flashing is commonly used to flash chimneys and involves two flashing pieces. The first piece, the base flashing, is meant to sit around the base of the chimney. The second piece, the counter-flashing itself, finds itself embedded in the chimney’s masonry.
This piece sits over the base flashing, ensuring the water doesn’t slip in behind it. Professional contractors generally use counter-flashing for a litany of other purposes, but it typically involves a second piece of flashing set off from the first.
Before you can learn to install roof flashing, you need to understand the three primary techniques involved. Each one is different and can be suitable for different areas of the roof. There are also flashing types that tend to correspond with a specific technique.
Step flashing ensures that water is properly directed away from the wall and winds up in the gutter. It is called step flashing because it is installed in—you guessed it—steps. The flashing involves layers of shingles between them, so the water gets poured down each step and down the roof.
Nails vs. Sealent
Using a sealant is key when installing roof flashing. Roofing professionals, generally of the old-school variety, still use nails while flashing. While nails can work, the roofer must choose whether to nail to the roof plane or to the vertical wall itself.
Nails
If the contractor decides to nail both, the flashing could deform under the pressure of shifting wood or brick. If they decide to nail only to the roof plane or the vertical wall, the flashing can then stay in place while the other materials contract and expand as the weather changes.
Weather change can wreak the most havoc. If the wrong materials are used or installed improperly, constant expansion and contraction can lead to bent or warped materials, making them more brittle until they finally break.
Cement
Roofing cement is generally accepted as the most common type of roofing sealant because it is meant to create a waterproof seal. Roofing professionals can use a trowel to apply it evenly so that it adheres properly.
Protecting Your Roof
Ultimately, installing flashing and applying a proper sealant is meant to protect your roof and its trouble areas from water and other damaging elements.
Those hard-to-reach areas can be the first to go without proper flashing, so it is imperative for the life of your roof that you have a flash that will expand and contract with the elements and divert the water off the roof.
Amateur roofers, who may not have the necessary knowledge or experience, can miss those tough-to-reach areas. Hiring a licensed and reputable roofing contractor ensures that those trouble areas do not worsen.
If not handled properly, water could pool around vents or the chimney and damage areas of the roof, creating discoloration and even leaks. If left unchecked, those leaks could cause structural damage.
A proper roof flashing can do wonders for protecting your roof from water damage and unnecessary wear and tear to those trouble areas on your roof.
